Nyūdōunsai Sanada, also known as Unsai, is the leader of the Sanada Clan of ninja dogs.
His pack makes their home in a tall thick tree, with him as the leader inside a giant treehole. His Clan's tradition is to prefer neutrality during the times of conflict. He can stand with two feet.
When he was only three years old, a young Ben brought a wounded Cross to him, because he knew Unsai to be a reliable and fair male. Unsai had to take good care of her and fell in love. Ben came to meet with Cross whenever he could, and Unsai soon realized that the Cross loved Ben and not him. When Cross healed, she left Unsai to join Ben in the Ou Army.
Unsai is light brown and white, dark brown snout mixed breed.
His eyebrows resemble the patterns and have top of the muzzle and on the front.
He have two scar in the right eyebrow and a two scar on the left front leg and one right.
He is peaceful, righteous and always willing to fight for those who want to live in peace even though wants to stay out of conflicts.
When he was younger, Ben saw him as a kind, caring and fair male.
Ginga Densetsu Weed: Orion
Nyūdōunsai's first true appearance was when he finds Kawasemi, one of his comrades, soaking wet along side a river. After checking on him, he saw some members from the Kurohabaki Clan who were responsible. He told his comrades to follow him and leapt across the river. When he was on the other side, he told the small group to get lost, and went back to the lair.
While Nyūdōunsai was resting inside the large tree, he was awaken by the racket from his comrades outside. When he looked out, he saw Orion and his friends under the tree. He became angry and leapt from the tree right in front of Orion, and was about to rip out his testicles when Orion escaped and bit him on the head.
Afterwards, it seemed that one of Orion's friends recognized him and said he was with Riki in the final battle with Akakabuto. Then, he took Orion, and showed him his land from the top of the giant tree and apologized for attacking him and his group.
Unsai recognizes the young pups strength and agrees to help him, telling him he feels the need to help the dogs who want to live in peace in Japan. Setsuma brings a wild boar and the pack eats. Unsai learns of Matheus and how he has taken over the Koga hideout.
Upon meeting the strange dog, Tenka, Unsai welcomes him but the mysterious dog tries to hypnotize him. Unsai seems under the spell at first, but instead only sneezes and says those tricks won't work on him.
In the final battle, Unsai arrives just in time to save Rigel from being thrown down the cliff by Masamune, setting the pup safely down with his brothers. After the death of Masamune, Unsai leaves with Tenka back to his land.
As Unsai leaves he says goodbye to Orion hoping to see him again.
Ginga: The Last Wars
Nyūdōunsai is doing a nightly patrol of his territory when he comes across a sleeping Reika, her children and Tonov. He is polite to her and asks if there is anything he can do to help. Reika tells him that the son of Akakabuto has attacked their home and wounded the leaders, killing many others. Nyūdōunsai decides to prepare his group for battle.
Whilst heading towards Ou, Unsai runs into Monsoon and a few of his kin, who initially attack him and his comrades. Unsai sees Monsoon as the second Akakabuto but is spared when the bear thinks he is not an Ou dog, and thus leaves him alone. Right after, Orion charges past Unsai and ignores his warning, running straight into Monsoon. Orion manages to scratch Monsoon's nose and is lucky to survive when the bear leaves him alone.
Sometime later, Unsai finds Kenshin being attacked by Monsoon and orders him to retreat, but this falls on deaf ears as the ninja dog attacks. Monsoon kills his two comrades and heavily injures Kenshin. Unsai goes to check on his friend, who dies from his injuries. Just then, Monsoon slams his giant paw down on Unsai, seemingly crushing his head. Unsai, however, escapes unharmed as he was caught between Monsoon's claws and was saved from death. He grabs Kenshin's body and retreats with the others.
Sometime later, a flood causes a wounded Ken to be washed into a river and the Ou army go to the location to find and save him. They each keep a watchful eye on the raging river, as Kawasemi dives in to find him.
After Ken is saved, Unsai heads with the others to find Monsoon and begin the attack. Unsai joins in the battle, shouting that this cannot be helped as they no longer have a choice. He yells at Sirius to come as there is no longer a point in thinking about Monsoon. Unsai leaps and bits into Monsoon's shoulder. Bon yells that he'll be killed if he attacks upfront. Unsai is swiped away by Monsoon, and then pursued by him. Unsai shouts that it's useless, and that they need the humans. Unsai realizes that Monsoon is only after him now, and wonders why he is so focused on hitting him. Unsai was still shaken from being knocked down, so his only choice was to run from Monsoon. Monsoon is targeting him because he saw Unsai as the one giving out the orders.
Unsai yells at Sirius to do something. Sirius doesn't respond, and Unsai demands to know if he wants to be eaten, as he will not tolerate being killed and eaten by the bears. As Monsoon continues to chase Unsai, Bon rushes in with the sickle, though without an idea on how to use it properly.
Unsai bites Monsoon, but knows it is futile as their fangs won't work on his thick fur and fat. Unsai backs away for a moment but sees Sirius take the sickle from Monsoon's side and run away with it. As he is distracted by Sirius, Unsai is slashed across the back of his right shoulder by Monsoon.
Unsai was too preoccupied with Sirius's baffling behavior that he took a blow from Monsoon and flew and bleeding. Unsai couldn't speak, he raised his voice to shout but nobody could hear him. He saw Akame get hit by Monsoon. He tell Akame that they're lucky to be laying down but he's feeling pitiful. He was just being conceited, he could do nothing and encourage Ohu youngsters and drive them to their deaths. He ask Akame to forgive him. He look at Orion and tell Sirius to help Orion. He tell him that he can't let Orion die and ask him what are he thinking.
Then, he sees Orion and Monsoon coming out of the forest with the red akita turning around to use the Battōga and saw in shock that Orion's attack didn't work.
Once the bears are gone, Unsai and others come up with a plan to defeat them. He sees Daisuke and Andy's owner and asked Orion if he knew the human. Then, Unsai collapses from his gaping wound Orion tried his best to relieve Unsai's tension but it was the arrival of the humans that did it. Akame and the others tried their best to come close him and convince the lord not to give up while Monsoon is still alive.
Knowing that Unsai trusted his body into the care of humans, he told Akame not to do anything rash while he went off to finish the bears. Unsai's condition begins to worsen, and he collapses. Daisuke and Hidetoshi know they need to take him back to the vets by themselves as they ran out of medicine for him. With the other dogs showing concern for him, Unsai is taken away on a stretcher. Whilst they are driving away, the other dogs feel defeated.
Sometime later, Unsai is doing much better resting in the barn with the rest of the injured soldiers. He calls Orion out for giving up on Sirius but the red akita is so happy to see him alive and thought it was over for him. He can see that the humans are being nice to him and the other dogs and Unsai says if he could live like this he could end his life right now but he told Orion it was just a bad joke.
Even Unsai believes even he could have a new purpose in life and says he won't die until Monsoon is sent to the underworld but with his condition Orion and Rigel couldn't use him anymore. So he turns his attention to Sirius knowing that Orion needs to stop him before he makes a serious mistake. Sometime later, along with the others he sees that Akame has recovered his sight.
Back at the barn Unsai hears from Gin what has happened back in Ohu and that Orion is handling things well for now. Then, soon Orion and Jerome arrive with the young pup looking anxious he hears Gin remind his grandson that he has to what six months for their injures to heal and he tries to make him understand that their feelings are the same. With that Weed watches Orion begins to leave but not before he hears Akame giving the young pup advice about training with the sickle.
After Orion's second departure, he hears Akame mention of the secret arts of fanged ninjas and that when it comes to mastering the techniques takes great discipline of the mind and body and that Akame himself took ten years to master and wondered if Orion was capable to doing it.
- Sanada was the surname of a Sengoku Jidai samurai clan, its most famous member being Sanada Yukimura.
- His ninja group, Sanada Jūganin-shū ("Sanada's Ten Fanged Shinobi"), is likely based off of the Sanada Ten Braves (Sanada Jūyūshi), a legendary, but most likely fictional group of ninja lead under Sanada Yukimura.
- In Yoshihiro Takahashi's interview in Finland, it was revealed that Nyūdōunsai apparently had relationship with Cross when they were younger but Cross left him after she met Ben.